The present invention relates to a damper disc and, more particularly, to a damper disc including torsion springs consisting of coaxially arranged compressible coil springs of large and small diameters.
Generally, damper discs have been employed in clutch discs in automobile and vibration absorbers between marine engines and reduction gears. A known damper disc comprises a hub splined to an output shaft, and a pair of annular side plates arranged at both sides of a radial flange of the hub. One of the side plates has a radially outer portion to which a torque is transmitted. The disc further comprises circumferentially extending torsion springs arranged in openings of the side plates and the hub flange for connecting the side plates and the flange, so that torque vibration in a driving mechanisms may be absorbed by compression and expansion of the springs, in other words, by relative torsion between the side plates and the flange. Some of the known damper discs include such torsion springs that are constructed of coaxially arranged compressible coil springs of large and small diameters. However, these double springs have fixed large and small diameters all along their lengths, respectively. Therefore, when the disc rotates at a high speed, the inner small springs, which are softer that the outer large springs, move outwardly along radii of the disc by centrifugal force, and contact the inner peripheries of the large springs. Consequently, both springs can not be smoothly compressed and expanded, and thus, the intended absorbing effect for the torque vibration can not be acquired. Further, said contact causes wear of the springs and reduces durability thereof.
Accordingly, it is an object of the invention to provide an improved damper disc, overcoming the above-noted disadvantages.
The essence of the present invention is to provide torsion springs including a compressible coil spring of which diameter gradually changes and is smallest at its axially middle.portion.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.